Common Skate
Dipturus batis
Dorsal View (♀)
APPEARANCE
Common Skate, Blue Skate, Grey Skate, Pocheteau Gris (Fr), Noriega
(Es).
• Large, up to 285cm total length.
SYNONYMS
• Upper surface olive-grey to brown.
Map base conforms with ICES grid squares.
Text & Illustrations © Shark Trust 2009
• Lower surface black in juveniles, fading with age.
• Juveniles have large orbital thorns.
NE ATL MED
DISTRIBUTION
The Common Skate was historically found across much of the
northeast Atlantic and Mediterranean (Luna, 2009). Its range has
been greatly reduced due to fishing pressure and it is now almost
extinct in the
Mediterranean
(Abdulla, 2004).
Around the UK,
individuals are
occasionally
reported from the
Irish Sea, Bristol
Channel and central
North Sea but it
would appear that
its range is now
effectively limited to
No Records
northwest Scotland
Occasional
and the Celtic Sea.
Range
(Dulvy et al., 2006).
• Variable pattern of light spots and dark blotches.
The Common Skate has a long and pointed snout giving the disc a
broadly rhombic shape with the front margins distinctly concave.
The dorsal surface of the disc is olive-grey or brown with a variable
pattern of light spots and dusky blotches. In sub-adults there is often
a marking on each pectoral fin resembling an eye spot (Whitehead et
al., 1986). The ventral surface of the disc is black in juveniles and fades
to grey as the animal matures (Neal et al., 2008). The mucus pores on
both sides of the disc are marked with black spots and short streaks
which are particularly numerous on the lower surface (Whitehead et
al., 1986).
Juveniles are smooth on both surfaces of the disc but often have
large orbital thorns. Adults are partly prickly on both the upper and
lower surfaces but have no thorns on the disc. There are two rows of
12-18 thorns along the tail (measured from the cloaca) and normally
one or two thorns between the dorsal fins. Often there are thorns
along the lower edges of the tail, particularly so in females (Luna,
2009).
They are the largest skate found in European waters with females
reaching a maximum total length of 285cm. They have between 40
and 56 rows of teeth and may live for 50-100 years (Luna, 2009; Dulvy
et al., 2006; Neal et al., 2008).
CR
Raja batis (Linnaeus, 1758), Raja macrorhynchus (Rafinesque, 1810),
Raja flossada (Risso, 1826), Raja intermedia (Parnell, 1837), Laeviraja
macrorhynchus (Bonaparte, 1839).
• Long, pointed snout.
RJB
COMMON NAMES
Ventral View (♀)
Supported by:
Common Skate
SIMILAR SPECIES
Dipturus nidarosiensis, Black Skate
Dipturus oxyrinchus, Long-nosed Skate
Rostroraja alba, White Skate
Dipturus batis,
Common Skate
Dipturus nidarosiensis,
Black Skate
Dipturus oxyrinchus,
Long-nosed Skate
Rostroraja alba,
White Skate
(Not to scale)
Text & Illustrations © Shark Trust 2009
Common Skate
Dipturus batis
TEETH
There are between 40–56 rows of
teeth (Luna, 2009).
ECOLOGY & BIOLOGY
HABITAT
Like most skates and rays, the Common Skate is a bottom
dwelling species that is found from coastal waters to a depth of
approximately 600m (1,970ft), although it is most commonly found
around 200m (670ft) (Dulvy et al., 2006). Unlike most other skate, it
is active both day and night (Luna, 2009).
EGGCASE
1. Very large, 120–250mm in length (Neal et al., 2008).
2. Distinct lateral keels.
3. Very deep anterior fields (Luna, 2009).
Similar eggcase to the Long-nosed Skate, Dipturus oxyrinchus.
DIET
The Common Skate has been recorded as feeding on several species
of skate (Raja spp.), dogfish (Squalus spp.), catshark (Scyliorhinus
spp.), anglerfish (Lophius spp.), gurnards (Dactyloptena spp.),
flatfishes, pilchards, herring (Clupea spp.) and scad (Trachurus spp.).
Lobsters, crabs and cephalopods (particular Eledone spp.) are also
important (Wheeler, 1969). It hunts actively, enveloping prey before
consuming it (Dulvy et al., 2006). Mid-water species are captured by
the skate propelling itself rapidly upward, enveloping and gripping
the fish before returning to the seabed to consume it (Wheeler,
1969).
REPRODUCTION
The Common Skate takes around 11 years to reach sexual maturity
at a length of around 150cm for males and 180cm for females.
Females only breed every other year, mating in spring and laying
up to 40 eggcases during summer which are deposited in sandy or
muddy flats (Neal et al., 2008). These eggcases are large, measuring
up to 25cm long (excluding the horns) and 15cm wide and are
covered with close-felted fibres (Neal et al., 2008; Dulvy et al.,
2006). They have been reported as being loose on the seabed and
occasionally secured between rocks. The embryos take between 2–5
months to develop depending on temperature and the juveniles are
born measuring 21-22cm long (Neal et al., 2008; Clark, 1926).
(Eggcase shown half actual size)
Text & Illustrations © Shark Trust 2009
Supported by:
COMMERCIAL IMPORTANCE
Historically important, the Common Skate has been targeted across
its range wherever and whenever it has been abundant. This has
lead to serious declines in stocks making it a financially unsound
species to target commercially. Until recently it was still caught
and landed by multispecies trawl fisheries operating over the vast
majority of its habitat (Dulvy et al., 2006). From January 2009 there
has been a prohibition on commercial fishers retaining this species
in ICES areas IIa, IIIa, IV, VI, VII, VIII & IX.
Common Skate
HANDLING AND THORN ARRANGEMENT
• Handle with care.
• Strong rows of thorns on midline.
• Thorns between dorsal fins.
The Common Skate is a popular species with recreational
anglers due to its large size but if these fish are returned alive there
is a good chance of them surviving (Catchpole et al., 2007). A catch
and release scheme involving recreational anglers in the Sound of
Mull, Scotland, generates an estimated £1,000,000 a year from a
stock of around 500 fish (Holt, 2005).
THREATS, CONSERVATION, LEGISLATION
The large size of the Common Skate allows it to be caught by most
fishing gear from birth, giving individuals little or no chance to
reach maturity in heavily fished areas (UK Biodiversity Action Plan;
1999). Combined with relatively late maturity and low population
increase rates, the Common Skate is extremely vulnerable to fishing
pressure. This has been seen in a drastic decline in populations
during the 20th century, particularly around the UK. It has been
extirpated from the majority of British coastal waters and is now
only regularly found in northwest Scotland, the Shetlands and the
Celtic Sea. French landings appear to be stable but this is likely to be
due to a redirection of the fishing effort from the continental shelf
into deeper water where the population may currently be stable
(Dulvy et al., 2006).
In 1999, the Common Skate was included on the UK Biodiversity
Action Plan (BAP) list. Though this does not provide any legal
protection for the species in itself, it includes provisions to work
towards European conservation legislation. Its main targets
included plans to stabilise populations in refuge areas by 2004 and
to facilitate the migration of animals from refuge populations to
areas where they are scarce or extinct (UK Biodiversity Action Plan;
1999).
In 2009, the Common Skate received protection from the
European Council in ICES areas IIa, IIIa, IV, VIIa-k, VIII and IX, meaning
that it cannot be retained by commercial fishers if captured. As
elasmobranchs have no swim bladder that can overinflate or
rupture, they are more likely to survive capture and release than
teleost fish (DEFRA; 2008). The mandatory release order is therefore
likely to significantly reduce the level of fishing mortality.
The vast majority of recreational anglers in the UK return any
Common Skate they catch alive. Some angling clubs and the
majority of charter boats tag and release Common Skate when
caught, an activity which provides a sustainable source of income
for many communities (Holt, 2005).
IUCN RED LIST ASSESSMENT
Critically Endangered (2006).
Critically Endangered in northeast Atlantic.
Text & Illustrations © Shark Trust 2009
TAXONOMIC NOTE
Since this factsheet was produced, genetic research has
revealed that the Common Skate, Dipturus batis, is in fact two
distinct species. These have been named D. intermedia and D.
flossada. Common names already in use for these species are the
Flapper Skate and Blue Skate respectively, although it remains to
be seen if these become widely accepted.
The two species appear to have different distributions and
biological characteristics. Of the two, D. intermedia is slower
growing and reaches a larger size. The first data published
suggests a size at 50% maturity of 197.5cm (♀) and 185.5cm (♂)
for D. intermedia, compared to 122.9cm (♀) and 115cm (♂) for D.
flossada. The largest positively identified specimen of D. flossada
was 143.2cm in length. It seems the maximum total length of
285cm previously attributed to D. batis must be D. intermedia.
While the ranges of the species overlap it appears that D.
intermedia is limited to west Scotland and west Ireland, with D.
flossada limted to the southern Irish and Celtic Seas and the Rockall
Trough. This appears to be closely related to temperature.
The most reliable means of distinguishing these species seems
to be the colour of the iris. In D. intermedia it is dark green/olive, in
D. flossada it is pale yellow. Other morphometric features to check
are the malar thorns, lateral tail thorns, interdorsal space and tooth
bases. Colouration can differ on the ventral surface and on the
centre of the wings. For a full discussion of these differences see
Iglésias et al., 2009, available online.
Common Skate
Dipturus batis
REFERENCES
ABDULLA, A. 2004. Status and Conservation of Sharks in the
Mediterranean Sea. IUCN Global Marine Programme.
CATCHPOLE, T. L., ENEVER, R., DORAN, S. 2007. Programme 21:
Bristol Channel Ray Survival. CEFAS. Lowestoft, UK.
CLARK, R. S. 1926. Rays and Skates. A Revision of the European
Species. Fishery Board for Scotland. HM Stationary Office.
Edinburgh, UK.
DEFRA. 2008. Impact Assessment of Tope Shark Protection
Measures. www.defra.gov.uk.
DULVY, N. K., NOTOBARTOLO DI SCIARA, G., SERENA, F., TINTI, F.,
UNGARO, N., MANCUSI, C., ELLIS, J. 2006. Dipturus batis. In:
IUCN 2008. 2008 IUCN Red List of Threatened Species. www.
iucnredlist.org.
HOLT, D. 2005 Common Skate Tagging Programme. The Scottish
Angling Homepage: www.catchalot.co.uk.
IGLÉSIAS, S. P., TOULHOAT, L., SELLOS, D. Y. 2009. Taxonomic
confusion and market mislabelling of threatened skates:
important consequences for their conservation status. Aquatic
Conserv: Mar. Freshw. Ecosyst. Published Online 2009.
LUNA, S. M. 2009. Dipturus batis. Blue Skate. Fishbase. www.
fishbase.org.
NEAL, K. J., PIZZOLLA, P. F., WILDING, C. M. 2008. Dipturus batis.
Common Skate. Marine Life Information Network: Biology
and Sensitivity Key Information Sub-programme [on-line].
Plymouth: Marine Biological Association of the United
Kingdom. www.marlin.ac.uk.
UK BIODIVERSITY ACTION PLAN. 1999. Species Action Plan:
Common Skate (Dipturus batis). www.ukbap.org.uk.
WHEELER, A. 1969. The Fishes of the British Isles and North-West
Europe. Macmillan and Co Ltd. London, UK.
WHITEHEAD, P. J. P., BAUCHOT, M. L., HUREAU, J. C., NIELSEN, J.,
Text: Richard Hurst.
Illustrations: Marc Dando.
Citation
Shark Trust; 2009. An Illustrated Compendium of Sharks, Skates, Rays
and Chimaera. Chapter 1: The British Isles. Part 1: Skates and Rays.
Any ammendments or corrections, please contact:
The Shark Trust
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Tel: 01752 672008/672020
Email: [email protected]
For more ID materials visit www.sharktrust.org/ID.
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Text & Illustrations © Shark Trust 2009